// Copyright (c) 2016, SolidCP
// SolidCP is distributed under the Creative Commons Share-alike license
// 
// SolidCP is a fork of WebsitePanel:
// Copyright (c) 2015, Outercurve Foundation.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
// - Redistributions of source code must  retain  the  above copyright notice, this
//   list of conditions and the following disclaimer.
//
// - Redistributions in binary form  must  reproduce the  above  copyright  notice,
//   this list of conditions  and  the  following  disclaimer in  the documentation
//   and/or other materials provided with the distribution.
//
// - Neither  the  name  of  the  Outercurve Foundation  nor   the   names  of  its
//   contributors may be used to endorse or  promote  products  derived  from  this
//   software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,  BUT  NOT  LIMITED TO, THE IMPLIED
// WARRANTIES  OF  MERCHANTABILITY   AND  FITNESS  FOR  A  PARTICULAR  PURPOSE  ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
// ANY DIRECT, INDIRECT, INCIDENTAL,  SPECIAL,  EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO,  PROCUREMENT  OF  SUBSTITUTE  GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)  HOWEVER  CAUSED AND ON
// ANY  THEORY  OF  LIABILITY,  WHETHER  IN  CONTRACT,  STRICT  LIABILITY,  OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE)  ARISING  IN  ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

using System;
using System.Collections.Generic;
using System.Text;

namespace SolidCP.Server.Utils
{
    /*
    * FreeSec: libcrypt for NetBSD 
    *  
    * Copyright (c) 1994 David Burren  
    * All rights reserved.  
    *  
    * Adapted for FreeBSD-2.0 by Geoffrey M. Rehmet  
    *      this file should now *only* export crypt(), in order to make  
    *      binaries of libcrypt exportable from the USA  
    *  
    * Adapted for FreeBSD-4.0 by Mark R V Murray  
    *      this file should now *only* export crypt_des(), in order to make  
    *      a module that can be optionally included in libcrypt.  
    *  
    * Redistribution and use in source and binary forms, with or without  
    * modification, are permitted provided that the following conditions  
    * are met:  
    * 1. Redistributions of source code must retain the above copyright  
    *    notice, this list of conditions and the following disclaimer.  
    * 2. Redistributions in binary form must reproduce the above copyright  
    *    notice, this list of conditions and the following disclaimer in the  
    *    documentation and/or other materials provided with the distribution.  
    * 3. Neither the name of the author nor the names of other contributors  
    *    may be used to endorse or promote products derived from this software  
    *    without specific prior written permission.  
    *  
    * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND  
    * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE  
    * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE  
    * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE  
    * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL  
    * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS  
    * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)  
    * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT  
    * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY  
    * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF  
    * SUCH DAMAGE.
    */

    public class BsdDES
    {
        byte[] IP = new byte[64] {
	        58, 50, 42, 34, 26, 18, 10,  2, 60, 52, 44, 36, 28, 20, 12,  4,
	        62, 54, 46, 38, 30, 22, 14,  6, 64, 56, 48, 40, 32, 24, 16,  8,
	        57, 49, 41, 33, 25, 17,  9,  1, 59, 51, 43, 35, 27, 19, 11,  3,
	        61, 53, 45, 37, 29, 21, 13,  5, 63, 55, 47, 39, 31, 23, 15,  7
        };

        byte[] inv_key_perm = new byte[64];
        byte[] key_perm = new byte[56] {
	        57, 49, 41, 33, 25, 17,  9,  1, 58, 50, 42, 34, 26, 18,
	        10,  2, 59, 51, 43, 35, 27, 19, 11,  3, 60, 52, 44, 36,
	        63, 55, 47, 39, 31, 23, 15,  7, 62, 54, 46, 38, 30, 22,
	        14,  6, 61, 53, 45, 37, 29, 21, 13,  5, 28, 20, 12,  4
        };

        byte[] key_shifts = new byte[16] {
	        1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
        };

        byte[] inv_comp_perm = new byte[56];
        byte[] comp_perm = new byte[48] {
	        14, 17, 11, 24,  1,  5,  3, 28, 15,  6, 21, 10,
	        23, 19, 12,  4, 26,  8, 16,  7, 27, 20, 13,  2,
	        41, 52, 31, 37, 47, 55, 30, 40, 51, 45, 33, 48,
	        44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32
        };

        /*
         *	No E box is used, as it's replaced by some ANDs, shifts, and ORs.
         */

        byte[,] u_sbox = new byte[8, 64];
        byte[,] sbox = new byte[8, 64] {
	        {
		        14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
		         0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
		         4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
		        15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
	        },
	        {
		        15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
		         3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
		         0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
		        13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
	        },
	        {
		        10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
		        13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
		        13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
		         1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
	        },
	        {
		         7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
		        13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
		        10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
		         3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
	        },
	        {
		         2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
		        14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
		         4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
		        11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
	        },
	        {
		        12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
		        10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
		         9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
		         4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13
	        },
	        {
		         4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
		        13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
		         1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
		         6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
	        },
	        {
		        13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
		         1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
		         7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
		         2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
	        }
        };


        byte[] un_pbox = new byte[32];
        byte[] pbox = new byte[32] {
	        16,  7, 20, 21, 29, 12, 28, 17,  1, 15, 23, 26,  5, 18, 31, 10,
	         2,  8, 24, 14, 32, 27,  3,  9, 19, 13, 30,  6, 22, 11,  4, 25
        };

        uint[] bits32 = new uint[32]
        {
	        0x80000000, 0x40000000, 0x20000000, 0x10000000,
	        0x08000000, 0x04000000, 0x02000000, 0x01000000,
	        0x00800000, 0x00400000, 0x00200000, 0x00100000,
	        0x00080000, 0x00040000, 0x00020000, 0x00010000,
	        0x00008000, 0x00004000, 0x00002000, 0x00001000,
	        0x00000800, 0x00000400, 0x00000200, 0x00000100,
	        0x00000080, 0x00000040, 0x00000020, 0x00000010,
	        0x00000008, 0x00000004, 0x00000002, 0x00000001
        };

        byte[] bits8 = new byte[8] { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };

        byte[] ascii64 = System.Text.ASCIIEncoding.ASCII.GetBytes(
             "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
        /*	  0000000000111111111122222222223333333333444444444455555555556666 */
        /*	  0123456789012345678901234567890123456789012345678901234567890123 */

        bool des_initialised = false;
        uint saltbits;
        uint old_salt;
        byte[] init_perm = new byte[64], final_perm = new byte[64];
        uint[] en_keysl = new uint[16], en_keysr = new uint[16];
        uint[] de_keysl = new uint[16], de_keysr = new uint[16];
        byte[,] m_sbox = new byte[4, 4096];
        uint[,] psbox = new uint[4, 256];
        uint[,] ip_maskl = new uint[8, 256], ip_maskr = new uint[8, 256];
        uint[,] fp_maskl = new uint[8, 256], fp_maskr = new uint[8, 256];
        uint[,] key_perm_maskl = new uint[8, 128], key_perm_maskr = new uint[8, 128];
        uint[,] comp_maskl = new uint[8, 128], comp_maskr = new uint[8, 128];
        uint old_rawkey0, old_rawkey1;



        uint AsciiToBin(char ch)
        {
            if (ch > 'z')
                return 0;
            if (ch >= 'a')
                return (uint)(ch - 'a' + 38);
            if (ch > 'Z')
                return 0;
            if (ch >= 'A')
                return (uint)(ch - 'A' + 12);
            if (ch > '9')
                return (0);
            if (ch >= '.')
                return (uint)(ch - '.');
            return 0;
        }

        void Init()
        {
            int inbit, obit;
            old_rawkey0 = old_rawkey1 = 0;
            saltbits = 0;
            old_salt = 0;
            const int bits28 = 4;
            const int bits24 = 8;

            /*
             * Invert the S-boxes, reordering the input bits.
             */
            for (int i = 0; i < 8; i++)
                for (int j = 0; j < 64; j++)
                {
                    int b = (j & 0x20) | ((j & 1) << 4) | ((j >> 1) & 0xf);
                    u_sbox[i, j] = sbox[i, b];
                }

            /*
             * Convert the inverted S-boxes into 4 arrays of 8 bits.
             * Each will handle 12 bits of the S-box input.
             */
            for (int b = 0; b < 4; b++)
                for (int i = 0; i < 64; i++)
                    for (int j = 0; j < 64; j++)
                        m_sbox[b, (i << 6) | j] =
                            (byte)((u_sbox[(b << 1), i] << 4) |
                            u_sbox[(b << 1) + 1, j]);

            /*
             * Set up the initial & final permutations into a useful form, and
             * initialise the inverted key permutation.
             */
            for (int i = 0; i < 64; i++)
            {
                init_perm[final_perm[i] = (byte)(IP[i] - 1)] = (byte)i;
                inv_key_perm[i] = 255;
            }

            /*
             * Invert the key permutation and initialise the inverted key
             * compression permutation.
             */
            for (int i = 0; i < 56; i++)
            {
                inv_key_perm[key_perm[i] - 1] = (byte)i;
                inv_comp_perm[i] = 255;
            }

            /*
             * Invert the key compression permutation.
             */
            for (int i = 0; i < 48; i++)
            {
                inv_comp_perm[comp_perm[i] - 1] = (byte)i;
            }

            /*
             * Set up the OR-mask arrays for the initial and final permutations,
             * and for the key initial and compression permutations.
             */
            for (int k = 0; k < 8; k++)
            {
                for (int i = 0; i < 256; i++)
                {
                    ip_maskl[k, i] = 0;
                    ip_maskr[k, i] = 0;
                    fp_maskl[k, i] = 0;
                    fp_maskr[k, i] = 0;
                    for (int j = 0; j < 8; j++)
                    {
                        inbit = 8 * k + j;
                        if ((i & bits8[j]) > 0)
                        {
                            if ((obit = init_perm[inbit]) < 32)
                                ip_maskl[k, i] |= bits32[obit];
                            else
                                ip_maskr[k, i] |= bits32[obit - 32];
                            if ((obit = final_perm[inbit]) < 32)
                                fp_maskl[k, i] |= bits32[obit];
                            else
                                fp_maskr[k, i] |= bits32[obit - 32];
                        }
                    }
                }
                for (int i = 0; i < 128; i++)
                {
                    key_perm_maskl[k, i] = 0;
                    key_perm_maskr[k, i] = 0;
                    for (int j = 0; j < 7; j++)
                    {
                        inbit = 8 * k + j;
                        if ((i & bits8[j + 1]) > 0)
                        {
                            if ((obit = inv_key_perm[inbit]) == 255)
                                continue;
                            if (obit < 28)
                                key_perm_maskl[k, i] |= bits32[obit + bits28];
                            else
                                key_perm_maskr[k, i] |= bits32[obit - 28 + bits28];
                        }
                    }
                    comp_maskl[k, i] = 0;
                    comp_maskr[k, i] = 0;
                    for (int j = 0; j < 7; j++)
                    {
                        inbit = 7 * k + j;
                        if ((i & bits8[j + 1]) > 0)
                        {
                            if ((obit = inv_comp_perm[inbit]) == 255)
                                continue;
                            if (obit < 24)
                                comp_maskl[k, i] |= bits32[obit + bits24];
                            else
                                comp_maskr[k, i] |= bits32[obit - 24 + bits24];
                        }
                    }
                }
            }

            /*
             * Invert the P-box permutation, and convert into OR-masks for
             * handling the output of the S-box arrays setup above.
             */
            for (int i = 0; i < 32; i++)
                un_pbox[pbox[i] - 1] = (byte)i;

            for (int b = 0; b < 4; b++)
                for (int i = 0; i < 256; i++)
                {
                    psbox[b, i] = 0;
                    for (int j = 0; j < 8; j++)
                    {
                        if ((i & bits8[j]) > 0)
                            psbox[b, i] |= bits32[un_pbox[8 * b + j]];
                    }
                }

            des_initialised = true;
        }

        void SetupSalt(uint salt)
        {
            uint obit, saltbit;
            int i;

            if (salt == old_salt)
                return;
            old_salt = salt;

            saltbits = 0;
            saltbit = 1;
            obit = 0x800000;
            for (i = 0; i < 24; i++)
            {
                if ((salt & saltbit) > 0)
                    saltbits |= obit;
                saltbit <<= 1;
                obit >>= 1;
            }
        }

        int SetKey(byte[] key)
        {
            if (!des_initialised)
                Init();

            uint rawkey0 = ntohl(BitConverter.ToUInt32(key, 0));
            uint rawkey1 = ntohl(BitConverter.ToUInt32(key, 4));

            if ((rawkey0 | rawkey1) > 0
                && rawkey0 == old_rawkey0
                && rawkey1 == old_rawkey1)
            {
                /*
                 * Already setup for this key.
                 * This optimisation fails on a zero key (which is weak and
                 * has bad parity anyway) in order to simplify the starting
                 * conditions.
                 */
                return 0;
            }
            old_rawkey0 = rawkey0;
            old_rawkey1 = rawkey1;

            /*
             *	Do key permutation and split into two 28-bit subkeys.
             */
            uint k0 = key_perm_maskl[0, rawkey0 >> 25]
               | key_perm_maskl[1, (rawkey0 >> 17) & 0x7f]
               | key_perm_maskl[2, (rawkey0 >> 9) & 0x7f]
               | key_perm_maskl[3, (rawkey0 >> 1) & 0x7f]
               | key_perm_maskl[4, rawkey1 >> 25]
               | key_perm_maskl[5, (rawkey1 >> 17) & 0x7f]
               | key_perm_maskl[6, (rawkey1 >> 9) & 0x7f]
               | key_perm_maskl[7, (rawkey1 >> 1) & 0x7f];
            uint k1 = key_perm_maskr[0, rawkey0 >> 25]
               | key_perm_maskr[1, (rawkey0 >> 17) & 0x7f]
               | key_perm_maskr[2, (rawkey0 >> 9) & 0x7f]
               | key_perm_maskr[3, (rawkey0 >> 1) & 0x7f]
               | key_perm_maskr[4, rawkey1 >> 25]
               | key_perm_maskr[5, (rawkey1 >> 17) & 0x7f]
               | key_perm_maskr[6, (rawkey1 >> 9) & 0x7f]
               | key_perm_maskr[7, (rawkey1 >> 1) & 0x7f];
            /*
             *	Rotate subkeys and do compression permutation.
             */
            int shifts = 0;
            for (int round = 0; round < 16; round++)
            {
                uint t0, t1;

                shifts += key_shifts[round];

                t0 = (k0 << shifts) | (k0 >> (28 - shifts));
                t1 = (k1 << shifts) | (k1 >> (28 - shifts));

                de_keysl[15 - round] =
                en_keysl[round] = comp_maskl[0, (t0 >> 21) & 0x7f]
                        | comp_maskl[1, (t0 >> 14) & 0x7f]
                        | comp_maskl[2, (t0 >> 7) & 0x7f]
                        | comp_maskl[3, t0 & 0x7f]
                        | comp_maskl[4, (t1 >> 21) & 0x7f]
                        | comp_maskl[5, (t1 >> 14) & 0x7f]
                        | comp_maskl[6, (t1 >> 7) & 0x7f]
                        | comp_maskl[7, t1 & 0x7f];

                de_keysr[15 - round] =
                en_keysr[round] = comp_maskr[0, (t0 >> 21) & 0x7f]
                        | comp_maskr[1, (t0 >> 14) & 0x7f]
                        | comp_maskr[2, (t0 >> 7) & 0x7f]
                        | comp_maskr[3, t0 & 0x7f]
                        | comp_maskr[4, (t1 >> 21) & 0x7f]
                        | comp_maskr[5, (t1 >> 14) & 0x7f]
                        | comp_maskr[6, (t1 >> 7) & 0x7f]
                        | comp_maskr[7, t1 & 0x7f];
            }
            return 0;
        }

        int DoDes(uint l_in, uint r_in, out uint l_out, out uint r_out, int count)
        {
            /*
             *	l_in, r_in, l_out, and r_out are in pseudo-"big-endian" format.
             */
            uint l, r;
            uint[] kl1, kr1;
            int kl, kr;
            uint f, r48l, r48r;
            int round;

            f = 0;
            l_out = r_out = 0;

            if (count == 0)
            {
                return 1;
            }
            else if (count > 0)
            {
                /*
                 * Encrypting
                 */
                kl1 = en_keysl;
                kr1 = en_keysr;
            }
            else
            {
                /*
                 * Decrypting
                 */
                count = -count;
                kl1 = de_keysl;
                kr1 = de_keysr;
            }

            /*
             *	Do initial permutation (IP).
             */
            l = ip_maskl[0, l_in >> 24]
              | ip_maskl[1, (l_in >> 16) & 0xff]
              | ip_maskl[2, (l_in >> 8) & 0xff]
              | ip_maskl[3, l_in & 0xff]
              | ip_maskl[4, r_in >> 24]
              | ip_maskl[5, (r_in >> 16) & 0xff]
              | ip_maskl[6, (r_in >> 8) & 0xff]
              | ip_maskl[7, r_in & 0xff];
            r = ip_maskr[0, l_in >> 24]
              | ip_maskr[1, (l_in >> 16) & 0xff]
              | ip_maskr[2, (l_in >> 8) & 0xff]
              | ip_maskr[3, l_in & 0xff]
              | ip_maskr[4, r_in >> 24]
              | ip_maskr[5, (r_in >> 16) & 0xff]
              | ip_maskr[6, (r_in >> 8) & 0xff]
              | ip_maskr[7, r_in & 0xff];

            while (count-- > 0)
            {
                /*
                 * Do each round.
                 */
                kl = 0;
                kr = 0;
                round = 16;
                while (round-- > 0)
                {
                    /*
                     * Expand R to 48 bits (simulate the E-box).
                     */
                    r48l = ((r & 0x00000001) << 23)
                        | ((r & 0xf8000000) >> 9)
                        | ((r & 0x1f800000) >> 11)
                        | ((r & 0x01f80000) >> 13)
                        | ((r & 0x001f8000) >> 15);

                    r48r = ((r & 0x0001f800) << 7)
                        | ((r & 0x00001f80) << 5)
                        | ((r & 0x000001f8) << 3)
                        | ((r & 0x0000001f) << 1)
                        | ((r & 0x80000000) >> 31);
                    /*
                     * Do salting for crypt() and friends, and
                     * XOR with the permuted key.
                     */
                    f = (r48l ^ r48r) & saltbits;
                    r48l ^= f ^ kl1[kl++];
                    r48r ^= f ^ kr1[kr++];
                    /*
                     * Do sbox lookups (which shrink it back to 32 bits)
                     * and do the pbox permutation at the same time.
                     */
                    f = psbox[0, m_sbox[0, r48l >> 12]]
                      | psbox[1, m_sbox[1, r48l & 0xfff]]
                      | psbox[2, m_sbox[2, r48r >> 12]]
                      | psbox[3, m_sbox[3, r48r & 0xfff]];
                    /*
                     * Now that we've permuted things, complete f().
                     */
                    f ^= l;
                    l = r;
                    r = f;
                }
                r = l;
                l = f;
            }
            /*
             * Do final permutation (inverse of IP).
             */
            l_out = fp_maskl[0, l >> 24]
                | fp_maskl[1, (l >> 16) & 0xff]
                | fp_maskl[2, (l >> 8) & 0xff]
                | fp_maskl[3, l & 0xff]
                | fp_maskl[4, r >> 24]
                | fp_maskl[5, (r >> 16) & 0xff]
                | fp_maskl[6, (r >> 8) & 0xff]
                | fp_maskl[7, r & 0xff];
            r_out = fp_maskr[0, l >> 24]
                | fp_maskr[1, (l >> 16) & 0xff]
                | fp_maskr[2, (l >> 8) & 0xff]
                | fp_maskr[3, l & 0xff]
                | fp_maskr[4, r >> 24]
                | fp_maskr[5, (r >> 16) & 0xff]
                | fp_maskr[6, (r >> 8) & 0xff]
                | fp_maskr[7, r & 0xff];
            return 0;
        }

        public string Crypt(string key)
        {
            // salt chars
            string salt_chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789./";

            // generate random salt - 2 symbols
            StringBuilder salt = new StringBuilder();
            Random rnd = new Random();
            for (int i = 0; i < 2; i++)
                salt.Append(salt_chars[rnd.Next(salt_chars.Length - 1)]);

            // call crypt
            return Crypt(key, salt.ToString());
        }

        public string Crypt(string key, string setting)
        {
            if (String.IsNullOrEmpty(setting) || setting.Length < 2)
                throw new ArgumentException("Salt must be at least 2 symbols", "setting");

            uint salt, l, r0, r1;
            int count;

            //u_char		*p, *q;
            //static char	output[21];
            byte[] output = new byte[13];

            if (!des_initialised)
                Init();

            /*
             * Copy the key, shifting each character up by one bit
             * and padding with zeros.
             */
            byte[] key_bytes = System.Text.ASCIIEncoding.ASCII.GetBytes(key);
            byte[] setting_bytes = System.Text.ASCIIEncoding.ASCII.GetBytes(setting);
            byte[] keybuf = new byte[8];

            for (int i = 0; i < keybuf.Length; i++)
                keybuf[i] = (i < key_bytes.Length) ? (byte)(key_bytes[i] << 1) : (byte)0;

            if (SetKey(keybuf) != 0)
                return null;

            /*
             * "old"-style:
             *	setting - 2 bytes of salt
             *	key - up to 8 characters
             */
            count = 25;

            salt = (AsciiToBin(setting[1]) << 6)
                 | AsciiToBin(setting[0]);

            output[0] = setting_bytes[0];
            /*
             * If the encrypted password that the salt was extracted from
             * is only 1 character long, the salt will be corrupted.  We
             * need to ensure that the output string doesn't have an extra
             * NUL in it!
             */
            output[1] = setting_bytes.Length > 1 ? setting_bytes[1] : output[0];

            int p = 2;

            SetupSalt(salt);
            /*
             * Do it.
             */
            if (DoDes(0, 0, out r0, out r1, count) != 0)
                return null;
            /*
             * Now encode the result...
             */
            l = (r0 >> 8);
            output[p++] = ascii64[(l >> 18) & 0x3f];
            output[p++] = ascii64[(l >> 12) & 0x3f];
            output[p++] = ascii64[(l >> 6) & 0x3f];
            output[p++] = ascii64[l & 0x3f];

            l = (r0 << 16) | ((r1 >> 16) & 0xffff);
            output[p++] = ascii64[(l >> 18) & 0x3f];
            output[p++] = ascii64[(l >> 12) & 0x3f];
            output[p++] = ascii64[(l >> 6) & 0x3f];
            output[p++] = ascii64[l & 0x3f];

            l = r1 << 2;
            output[p++] = ascii64[(l >> 12) & 0x3f];
            output[p++] = ascii64[(l >> 6) & 0x3f];
            output[p++] = ascii64[l & 0x3f];

            return System.Text.ASCIIEncoding.ASCII.GetString(output);
        }

        uint ntohl(uint n)
        {
            return ((n & 0xFF) << 24) | ((n & 0xFF00) << 8) | ((n & 0xFF0000) >> 8) | ((n & 0xFF000000) >> 24);
        }
    }
}
